EP1548721B1 - Optisches aufzeichnungsmedium - Google Patents

Optisches aufzeichnungsmedium Download PDF

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Publication number
EP1548721B1
EP1548721B1 EP03748676A EP03748676A EP1548721B1 EP 1548721 B1 EP1548721 B1 EP 1548721B1 EP 03748676 A EP03748676 A EP 03748676A EP 03748676 A EP03748676 A EP 03748676A EP 1548721 B1 EP1548721 B1 EP 1548721B1
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Prior art keywords
layer
diffusion preventing
preventing layer
recording medium
optical recording
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English (en)
French (fr)
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EP1548721A4 (de
EP1548721A1 (de
Inventor
Kenjirou c/o Mitsubishi Kagaku Media Co. Ltd. KIYONO
Jun c/o Mitsubishi Kagaku Media Co. Ltd. KANEHIRA
Akio c/o Mitsubishi Kagaku Media Co. Ltd. OKAMURO
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Mitsubishi Chemical Media Co Ltd
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Mitsubishi Chemical Media Co Ltd
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/257—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/2403—Layers; Shape, structure or physical properties thereof
    • G—PHYSICS
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    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
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    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G—PHYSICS
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    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
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    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
    • G11B2007/24302—Metals or metalloids
    • G11B2007/24314—Metals or metalloids group 15 elements (e.g. Sb, Bi)
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    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
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    • G11B2007/25705—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials
    • G11B2007/25706—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials containing transition metal elements (Zn, Fe, Co, Ni, Pt)
    • G—PHYSICS
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    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
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    • G11B7/257—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers
    • G11B2007/25705—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials
    • G11B2007/25708—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials containing group 13 elements (B, Al, Ga)
    • G—PHYSICS
    • G11—INFORMATION STORAGE
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    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
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    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/257—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers
    • G11B2007/25705—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials
    • G11B2007/2571—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials containing group 14 elements except carbon (Si, Ge, Sn, Pb)
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/257—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers
    • G11B2007/25705—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials
    • G11B2007/25715—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials containing oxygen
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/258—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of reflective layers
    • G11B7/259—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of reflective layers based on silver
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/258—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of reflective layers
    • G11B7/2595—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of reflective layers based on gold
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/21—Circular sheet or circular blank

Definitions

  • the present invention relates to an optical recording medium, particularly an optical recording medium excellent in rewriting cyclability and storage stability.
  • a phase change type optical recording medium utilizing the phase transfer between crystalline and amorphous is known as one of optical recording media capable of recording, retrieving or erasing information by irradiation with light such as a laser beam.
  • the structure of such a phase change type optical recording medium usually takes a multilayer structure as shown in Fig. 1 . Namely, on a substrate 1 having concavo-convex, located on the incident side of a laser beam, a phase change recording layer 3 (in this specification, the phase change recording layer may sometimes be referred to simply as a recording layer) made of a phase change material which is usually sandwiched by protective layers 2 and 4 made of a dielectric material such as a mixture of ZnS and SiO 2 , is formed.
  • a reflective layer 5 composed mainly of Au, Al, Ag or the like as the main component, which serves as a heat diffusion layer, is formed.
  • an overcoat layer 6 made of an ultraviolet curable resin or the like, is formed.
  • a Ge 2 Sb 2 Te 5 system having a composition close to an intermetallic compound, or a system having a composition close to Sb 0.7 Te 0.3 , eutectic point of Sb-Sb 2 Te 3 , as the main component may be mentioned.
  • phase change-optical recording medium The recording principle of such a phase change-optical recording medium is as follows. After the film formation, the above recording layer is amorphous, and accordingly, the reflectance of the phase change type optical recording medium is low. Therefore, after formation of the recording layer, the phase change type optical recording medium is irradiated with a laser beam to heat the recording layer to carry out the step of crystallizing the recording layer over the entire surface of the substrate to let the entire surface of the phase change type optical recording medium have a high reflectance (in this specification, this step may be referred to as initial crystallization). Such an initially crystallized phase change type optical recording medium is locally irradiated with a laser beam, so that the recording layer is melted and quenched and thereby changed to an amorphous state.
  • the optical nature of the recording layer changes, whereby information will be recorded.
  • Retrieving of information is carried out by irradiating a laser beam weaker than during the recording, and detecting the difference in the optical nature between the crystalline state and the amorphous state as a difference in the reflectance.
  • Rewriting of information is carried out by directly rewriting a record mark present in the recording layer to a new record mark by irradiating the optical recording medium with a laser beam having a writing peak power superposed on an erasing power with a low energy to cause crystallization.
  • a method has been proposed by WO 97/34298 (cf. the preamble of claims 1 and 5) to provide a single layer of a diffusion preventing layer made of e.g. GeN between the recording layer and the protective layer.
  • a diffusion preventing layer of e.g. GeN has a function to prevent mutual diffusion of constituting atoms between the protective layer and the recording layer, and it is thereby intended to improve the number of repetitive rewriting times for rewriting information.
  • an optical recording medium which is capable of recording information of at least 20 GB in a CD size with a diameter of 12 cm by using a blue color laser having a wavelength of 405 nm and an object lens having a numerical aperture NA as large as 0.85 ( Jpn. J. Appl. Phys. Vol. 39 (2000) pp. 756-761, Part 1, No 2B, Feb. 2000 ).
  • the wavelength is short, and the numerical aperture of the object lens is large, whereby it is necessary to maintain a margin for the inclination (tilt) of the optical recording medium. Accordingly, as opposed to the conventional substrate side incident type layered structure as shown in Fig.
  • this optical recording medium is designed, as shown in Fig. 2(a) to have a reflective layer 5 between a substrate 1 and a recording layer 3 and to carry out recording and retrieving by applying a laser beam to the phase change recording layer from the side of the recording layer 3 opposite to the substrate 1 side.
  • Such an optical recording medium is commonly called "film side incident type optical recording medium”.
  • an optical recording medium film side incident type optical recording medium
  • the deterioration of the optical recording medium due to repeated rewriting appears more distinctly.
  • this deterioration is attributable to mutual diffusion of constituting atoms between the recording layer 3 and the protective layer 4 located at the incident side. It has been found that the mutual diffusion of constituting atoms between the recording layer 3 and the protective layer 4 becomes particularly distinct when the protective layer 4 contains sulfur.
  • the present inventors have attempted to suppress the mutual diffusion of constituting atoms between the recording layer 3 and the protective layer 4 by using the technique disclosed in the above Patent Document 1. Namely, as shown in Fig. 2(b) , a single layer of a diffusion preventing layer 13 was formed between the recording layer 3 and the protective layer 4, and the proportion of the gas component such as nitrogen in this diffusion preventing layer 13 was changed in detail.
  • the optical recording medium employing the above-mentioned single layer of a diffusion preventing layer 13 did not become an optical recording medium wherein the number of rewritable times and the storage stability are balanced at a higher level.
  • the present invention has been made to effectively solve such problems, and its object is to take a balance of the rewriting cyclability and the storage stability of the optical recording medium at a higher level than the conventional optical recording medium.
  • the present inventors have conducted an extensive study in view of the above situation, and as a result, have found it possible to take a balance of a rewriting cyclability and the storage stability at a higher level than the conventional optical recording medium, by separating the functions of the diffusion preventing layer present between the recording layer and the protective layer as between the recording layer side and the protective layer side, and thus have accomplished the present invention.
  • the first gist of the present invention resides in an optical recording medium comprising a reflective layer and a phase change recording layer formed in this order on a substrate, so that recording and retrieving information is carried out by applying a laser beam to the phase change recording layer from the side of the phase change recording layer opposite to the substrate side, a diffusion preventing layer is formed in contact with the phase change recording layer on the side of the phase change recording layer opposite to the substrate side, a protective layer containing sulfur, is formed in contact with the diffusion preventing layer, the diffusion preventing layer is constituted by at least two layers, which comprise a non-gas element and nitrogen and/or oxygen as the main components, and when among at least two layers constituting the diffusion preventing layer, the layer in contact with the phase change recording layer is designated as a first diffusion preventing layer, and the layer in contact with the protective layer is designated as a second diffusion preventing layer, the amount (atomic%) of nitrogen and/or oxygen contained in the second diffusion preventing layer is larger than the amount (atomic%) of nitrogen and/or oxygen contained in the first diffusion
  • the second gist of the present invention resides in an optical recording medium comprising a reflective layer and a phase change recording layer formed in this order on a substrate, so that recording and retrieving information is carried out by applying a laser beam to the phase change recording layer from the side of the phase change recording layer opposite to the substrate side, a diffusion preventing layer is formed in contact with the phase change recording layer on the side of the phase change recording layer opposite to the substrate side, a protective layer containing sulfur, is formed in contact with the diffusion preventing layer, the diffusion preventing layer comprises a non-gas element and nitrogen and/or oxygen as the main components, and the content (atomic%) of nitrogen and/or oxygen at the interface between the diffusion preventing layer and the protective layer is larger than the content (atomic%) of nitrogen and/or oxygen at the interface between the diffusion preventing layer and the phase change recording layer.
  • the proportion of the gas component such as nitrogen present in the diffusion preventing layer increases, the mutual diffusion of constituting atoms between the recording layer and the protective layer will be effectively suppressed when rewriting is carried out repeatedly, whereby the rewriting cyclability will be improved, but peeling is likely to take place between the recording layer and the diffusion preventing layer during a high temperature and high humidity storage, whereby the storage stability (storage stability) of the optical recording medium tends to deteriorate.
  • the protective layer located on the substrate side of the recording layer is in contact with a reflective layer having a high heat dissipation property, while the protective layer located on the incident side is not in contact with a member having a high heat dissipation property. Therefore, if rewriting is carried out repeatedly on such a film side incident type optical recording medium, the thermal storage of the protective layer located on the incident side tends to be large, whereby diffusion of constituting atoms of the protective layer tends to take place. Accordingly, it is preferred to increase the content of the gas component such as nitrogen in the diffusion preventing layer to be inserted between the recording layer and the protective layer located on the incident side.
  • the gas component such as nitrogen in the diffusion preventing layer
  • the protective layer (on the substrate side), the diffusion preventing layer (on the substrate side), the recording layer, the diffusion preventing layer (on the incident:side) and the protective layer (on the incident side) are laminated in this order on the substrate by a sputtering method, peeling tends to occur between the recording layer and the diffusion preventing layer (on the incident side) to be formed after the recording layer.
  • the reason for such tendency is considered to be as follows.
  • the protective layer (on the substrate side), the diffusion preventing layer (on the substrate side), the recording layer, the diffusion preventing layer (on the incident side) and the protective layer (on the incident side) are formed in this order on the substrate by a sputtering method, at the time of forming the recording layer on the diffusion preventing layer (on the substrate side), an excess gas component (such as nitrogen or oxygen) on the diffusion preventing layer (on the substrate side) will be evacuated by the evacuation of the chamber before the formation of the recording layer, whereby the residual gas at the interface between the diffusion preventing layer (on the substrate side) and the recording layer, tends to be extremely small.
  • an excess gas component such as nitrogen or oxygen
  • a gas such as nitrogen will be blown to the surface of the recording layer, whereby an excess gas component such as nitrogen tends to enter into the interface between the recording layer and the diffusion preventing layer (on the incident side). It is conceivable that under these conditions, peeling tends to take place between the recording layer and the diffusion preventing layer (on the incident side) during a high temperature and high humidity storage. Accordingly, with a view to suppressing peeling, it is advisable to reduce the content of the gas component such as nitrogen in the diffusion preventing layer (on the incident side) to be inserted between the recording layer and the protective layer on the incident side, as far as possible.
  • the film side incident type optical recording medium ( ⁇ ) from the viewpoint of carrying out repetitive rewriting satisfactorily, it is preferred to increase the content of the gas component such as nitrogen in the diffusion preventing layer to be inserted between the recording layer and the protective layer located on the incident side, while ( ⁇ ) in consideration of peeling by a high temperature and high humidity storage, it is preferred to minimize the content of nitrogen in the diffusion preventing layer to be inserted between the recording layer and the protective layer located on the incident side. Namely, with the film side incident type optical recording medium, the trade off of the above ( ⁇ ) and the above ( ⁇ ) becomes especially distinct. Accordingly, with the film side incident type optical recording medium, it is extremely difficult to satisfy both prevention of mutual diffusion of constituting atoms between the recording layer and the protective layer and the storage stability (prevention of peeling at the diffusion preventing layer).
  • the present inventors have found it possible to obtain an optical recording medium satisfying the storage stability and the rewriting cyclability at a high level with a film side incident type optical recording medium, by proficiently utilizing the phenomenon that the rewriting cyclability and the storage stability are in a trade off relation depending upon the degree of the content of the gas content such as nitrogen or oxygen in the diffusion preventing layer.
  • the diffusion preventing layer formed between the recording layer and the protective layer on the incident side if the content of the gas component is reduced in the diffusion preventing layer in the vicinity of the interface with the recording layer, the adhesion between the recording layer and the diffusion preventing layer is secured, whereby the storage stability will be made satisfactory, while if the content of the gas component is increased in the diffusion preventing layer in the vicinity of the interface with the protective layer, the mutual diffusion of constituting atoms between the recording layer and the protective layer will be suppressed, whereby the rewriting cyclability will be made satisfactory.
  • the present invention has been accomplished on the basis of such discoveries.
  • excellent in the storage stability means that no substantial peeling will be formed even after the storage under a high temperature and high humidity condition. Such peeling after the storage under a high temperature and high humidity condition, can be observed by an optical microscope. Further, in order to more strictly evaluate whether or not substantial peeling has taken place after the storage under a high temperature and high humidity condition, an increase of the bit error after the storage under a high temperature and high humidity condition, may be measured.
  • peeling will be a local defect which increases an error rate.
  • the size of the peeled area is sufficiently small, and the number of peeled portions is sufficiently small, such will not appear as an increase of the error rate.
  • the optical recording medium will be excellent in the storage stability.
  • ⁇ /(2NA) will be an error, where ⁇ is the wavelength for recording and retrieving, and NA is the numerical aperture of the object lens.
  • the error may be corrected by error correction by a Reed-Solomon symbol and the like, although such may depend also on the format and the like. Accordingly, peeling with a size at a level of ⁇ /(2NA), can be error-corrected, if it is dispersed with an average distance at a level of 100 ⁇ /(2NA). However, even in a case where the number of peeled portions is sufficiently small, if the size of one peeled area exceeds 50 ⁇ m, correction will be impossible.
  • the present invention it is possible to obtain an optical recording medium which simultaneously satisfies the recording characteristics and the storage stability at a higher level than the conventional optical recording medium. Especially with a film side incident type optical recording medium capable of high density recording, the rewriting cyclability and the storage stability under a high temperature and high humidity condition, can be remarkably improved.
  • the optical recording medium in the first embodiment of the present invention is an optical recording medium comprising a reflective layer and a phase change recording layer formed in this order on a substrate, so that recording and retrieving information is carried out by applying a laser beam to the phase change recording layer from the side of the phase change recording layer opposite to the substrate side, characterized in that:
  • the diffusion preventing layer is constituted by at least two layers as described above, whereby the rewriting cyclability and the storage stability for an optical recording medium can be satisfied simultaneously.
  • the diffusion preventing layer to be formed between the recording layer and the protective layer is a layer which is present between the recording layer and the protective layer and which prevents the mutual diffusion of constituting atoms or a chemical reaction between the recording layer and the protective layer and consequently improves the number of repetitive rewriting times of the optical recording medium.
  • “comprising a non-gas element and nitrogen and/or oxygen as the main components” means that the total content of the non-gas element and nitrogen and/or oxygen is at least 50 atomic% in the diffusion preventing layer.
  • the first diffusion preventing layer and the second diffusion preventing layer are formed for preventing diffusion of such components, as the main object.
  • the first diffusion preventing layer and the second diffusion preventing layer are made so that the non-gas element and nitrogen and/or oxygen will be the main components, while the composition of the first diffusion preventing layer is adjusted so that mutual diffusion of constituting elements with the recording layer will not take place, and the adhesion with the recording layer will be improved, and the composition of the second diffusion preventing layer is made to be one whereby no mutual diffusion of constituting elements with the protective layer will take place, whereby, as a result, it is possible to simultaneously satisfy the prevention of diffusion of constituting elements between the recording layer and the protective layer and the adhesion of the recording layer and the diffusion preventing layer.
  • the diffusion preventing layer is constituted by at least two layers containing the non-gas element and nitrogen and/or oxygen as the main components.
  • the diffusion preventing layer is made to be at least two layers having the first diffusion preventing layer and the second diffusion preventing layer.
  • Its layered structure is not particularly limited so long as it is capable of effectively preventing diffusion of constituting elements between the recording layer and the protective layer even when rewriting is carried out repeatedly.
  • the diffusion preventing layer is constituted by two layers of the first diffusion preventing layer and the second diffusion preventing layer.
  • the diffusion preventing layer is preferably constituted by the first diffusion preventing layer and the second diffusion preventing layer.
  • the diffusion preventing layer to be used for an optical recording medium is required to satisfy three points i.e. free from diffusion of constituting elements to the recording layer, free from diffusion of constituting elements to a protective layer, and free from peeling from the recording layer.
  • the diffusion preventing layer is made to have a double layered structure
  • the first diffusion preventing layer in contact with the recording layer is simply required to have a function to be free from mutual diffusion of constituting elements to the recording layer and to be free from peeling from the recording layer
  • the second diffusion preventing layer in contact with the protective layer is simply required to have a function to prevent diffusion of constituting elements to the protective layer.
  • the diffusion preventing layer is made to have a double layered structure to separate the functions of the diffusion preventing layers, whereby there will be a merit in that freeness to select the material and the layered structure will be widened.
  • the non-gas element contained in each of them is preferably made to be the same.
  • the non-gas element it is possible to prepare the first diffusion preventing layer and the second diffusion preventing layer from the same target, whereby it is possible to simplify the production.
  • the diffusion preventing layer is constituted by two layers of the first diffusion preventing layer and the second diffusion preventing layer, wherein the non-gas elements to be used in the respective layers are the same.
  • the present invention is by no means restricted to the following specific example.
  • Figs. 3(a) to (d) are diagrammatical views showing examples of the layered structures of optical recording media according to the first embodiment of the present invention.
  • the optical recording medium in Fig. 3(a) comprises a reflective layer 5, a protective layer 2, a recording layer 3, a first diffusion preventing layer 10, a second diffusion preventing layer 11, a protective layer 4 and a light transmitting layer 9 laminated in this order on a substrate 1, and a laser beam 100 is applied to the optical recording medium from the upper surface of the light transmitting layer 9.
  • the protective layer 4 tends to have a very large thermal storage by irradiation with a laser during recording, as it is not in contact with a reflective layer having a high heat dissipation property. Accordingly, with an optical recording medium having a construction as in Fig. 2(a) , diffusion of constituting atoms between the recording layer 3 and the protective layer 4 by repetitive rewriting will be distinct.
  • the recording density is made to be higher density than the conventional optical recording medium, whereby a little deterioration of the optical recording medium tends to be more distinct. Accordingly, in the above film side incident type optical recording medium, deterioration of the signal quality of the optical recording medium caused by the mutual diffusion of constituting atoms between the recording layer 3 and the protective layer 4 by repetitive rewriting will be particularly distinct.
  • the optical recording medium may be made to be one having a structure as shown in Fig. 2(b) wherein a diffusion preventing layer 13 is formed between the recording layer 3 and the protective layer 4.
  • the thermal storage of the protective layer 4 on the incident side of a short wavelength laser 100 is larger, whereby the diffusion preventing layer 13 on the incident side is desired to have a stronger function to prevent the mutual diffusion of constituting elements between the recording layer 3 and the protective layer 4.
  • the diffusion preventing layer 13 is constituted by a nitride, an oxide or a oxynitride, this means to increase the content of nitrogen and/or oxygen in the diffusion preventing layer 13.
  • the diffusion preventing layer 13 is formed after the recording layer 3, and if the content of nitrogen and/or oxygen is increased, peeling between the recording layer 3 and the diffusion preventing layer 13 tends to occur more readily. Namely, for the film side incident type optical recording medium capable of recording with a higher density, it becomes very important to take a balance between the storage stability and the stability during repetitive rewriting. Accordingly, the effects by functional separation of the diffusion preventing layer as shown in Figs. 3(a) to (d) will be remarkable in an application to the film side incident type optical recording medium.
  • the first diffusion preventing layer and the second diffusion preventing layer comprise a non-gas element and nitrogen and/or oxygen, as the main components, and the non-gas elements in the first diffusion preventing layer and the second diffusion preventing layer are the same.
  • the non-gas elements to be contained in the first diffusion preventing layer and the second diffusion preventing layer may be of one type or two or more types.
  • first diffusion preventing layer and the second diffusion preventing layer either nitrogen, oxygen, or nitrogen and oxygen, may be present together with the non-gas elements. However, it is preferred to employ either nitrogen, or nitrogen and oxygen, and more preferred to employ nitrogen.
  • the non-gas element may be any element which is not a gas or liquid in the state of a single substance or molecule at a normal temperature under a normal pressure (i.e. at 25°C under 1 atm), and an element such as hydrogen (H), nitrogen (N), oxygen (O), fluorine (F), chlorine (Cl), bromine (Br), helium (He), neon (Ne), argon (Ar), krypton (Kr) or xenon (Xe) is excluded.
  • non-gas element it is preferred to employ at least one element selected from the group consisting of Si, Ge, Al, Ti, Ta, Cr, Mo, Sb, Sn, Nb, Y, Zr and Hf.
  • Nitrides, oxides or oxynitrides of these non-gas elements are stable, whereby the storage stability of the optical recording medium will be improved.
  • Such non-gas elements may be employed in a plurality. Specifically, a plurality of the above elements, or a plurality of the above elements and non-gas elements other than the above elements, may be employed.
  • the non-gas element more preferred is Si, Ge, Al or Cr which is highly transparent and excellent in adhesion.
  • the non-gas element to be used particularly preferred is Ge and/or Cr.
  • a nitride or oxide of the single substance of the non-gas element may be mentioned as the material constituted by the non-gas element and nitrogen and/or oxygen. More specifically, compositions in the vicinity of Si 3 N 4 , Ge 3 N 4 , CrN, AlN, SiO 2 , GeO, GeO 2 , CrO, Cr 2 O 3 , AL 2 O 3 , etc, may be mentioned. Among them, it is preferred to use Si 3 N 4 , Ge 3 N 4 or AlN from such a viewpoint that the effect for preventing diffusion for the eutectic recording layer, is higher. Further, in a case where an oxynitride is to be employed, a mixture of the above-mentioned nitride and oxide of the single substance of the non-gas element, may be employed.
  • a nitride or oxide of a composite of non-gas elements may be mentioned.
  • a typical example employing Ge-N may be one containing Al, B, Ba, Bi, C, Ca, Ce, Cr, Dy, Eu, Ga, In, K, La, Mo, Nb, Ni, Pb, Pd, Si, Sb, Sn, Ta, Te, Ti, V, W, Yb, Zn, Zr, etc., together with Ge, like Ge-Si-N, Ge-Sb-N, Ge-Cr-N, Ge-Al-N, Ge-Mo-N or Ge-Ti-N.
  • Ge-Cr-N Ge-Al-N or Ge-Mo-N
  • a mixture of a nitride and an oxide of the above-mentioned non-gas element composites may be employed.
  • the total content of the non-gas element and nitrogen and/or oxygen in the first diffusion preventing layer 10 and in the second diffusion preventing layer 11, is usually at least 70 atomic%, preferably at least 90 atomic%, more preferably at least 95 atomic%, most preferably at least 99 atomic%. In this manner, it is possible to effectively suppress peeling from the recording layer, and it is possible to improve the rewriting cyclability.
  • the first diffusion preventing layer 10 and the second diffusion preventing layer 11 may contain other elements within a range not to impair the characteristics of the layer, as the case requires.
  • the content of such elements is preferably at most 10 atomic%, more preferably at most 5 atomic%, particularly preferably at most 1 atomic%.
  • such an element is not particularly limited, but when it is an element having a nature which diffuses in the layer, such as e.g. sulfur, its content is preferably at most 1 atomic%.
  • the content of nitrogen and/or oxygen in the first diffusion preventing layer 10 is usually at least 3 atomic%, preferably at least 5 atomic%, more preferably at least 10 atomic%. Within such a range, it is possible to obtain a diffusion preventing layer having an optically small absorption. On the other hand, the content of nitrogen and/or oxygen in the first diffusion preventing layer 10 is usually at most 50 atomic%, preferably at most 45 atomic%, more preferably at most 40 atomic%. Within such a range, it is possible to prevent peeling between the recording layer and the first diffusion preventing layer 10.
  • the content of nitrogen and/or oxygen in the second diffusion preventing layer 11 is usually at least 40 atomic%, while it is usually at most 70 atomic%, preferably at most 65 atomic%, more preferably at most 60 atomic%. Within such a range, it is possible to suppress the chemical reaction and diffusion of constituting atoms between the protective layer and the second diffusion preventing layer 11.
  • the content (atomic%) of nitrogen and/or oxygen contained in the second diffusion preventing layer is made larger than the content (atomic%) of nitrogen and/or oxygen contained in the first diffusion preventing layer 10.
  • the ratio of the contents of nitrogen and/or oxygen contained respectively in the first diffusion preventing layer 10 and the second diffusion preventing layer 11, i.e. (content of nitrogen and/or oxygen in the first diffusion preventing layer 10)/(content of nitrogen and/or oxygen in the second diffusion preventing layer 11), is usually smaller than 1, preferably at most 0.8, more preferably at most 0.6, further preferably at most 0.5, most preferably at most 0.4. Within such a range, the balance of the rewriting cyclability and the storage stability of the optical recording medium will be good.
  • the analyses of the compositions of the first diffusion preventing layer 10 and the second diffusion preventing layer 11 can be carried out by a combination of an Auger electron spectrophotometry (AES), a Rutherford backscattering method (RBS), an induction coupling high frequency plasma photometry (ICP), etc. And, by such analyses of the compositions, the contents (atomic%) of nitrogen and/or oxygen in the first diffusion preventing layer 10 and the second diffusion preventing layer 11, can be obtained.
  • AES Auger electron spectrophotometry
  • RBS Rutherford backscattering method
  • ICP induction coupling high frequency plasma photometry
  • the thicknesses of the first diffusion preventing layer 10 and the second diffusion preventing layer 11 are usually at least 1 nm, respectively. Within such a range, it becomes possible to suppress diffusion of sulfur even in a case where ZnS-SiO 2 is employed, which is widely used for a protective layer. Further, if the film thickness is excessively thin, a uniform diffusion preventing layer may not be obtained.
  • the thickness of the first diffusion preventing layer 10 and the second diffusion preventing layer 11 is usually at most 20 nm, preferably at most 10 nm, more preferably at most 7 nm, further preferably at most 5 nm, particularly preferably at most 3 nm.
  • the ratio of the thickness of the first diffusion preventing layer 10 to the thickness of the second diffusion preventing layer 11, i.e. (thickness of the first diffusion preventing layer 10)/(thickness of the second diffusion preventing layer 11), is usually at least 0.1, preferably at least 0.2, more preferably at least 0.3, while it is usually at most 10, preferably at most 5, more preferably at most 3.
  • the first diffusion preventing layer 10 and the second diffusion preventing layer 11 can, respectively, be produced by a sputtering method wherein a very small amount of Ar gas is circulated in a vacuum chamber to a predetermined vacuum pressure, and a voltage is applied to a target made of a nitride, oxide or oxynitride of a simple substance of the non-gas element having a different content of nitrogen and/or oxygen, or a nitride, oxide or oxynitride of a composite of non-gas elements, having a different content of nitrogen and/or oxygen to carry out discharge and film forming.
  • the first diffusion preventing layer 10 and the second diffusion preventing layer 11 may be formed by a reactive sputtering method wherein in a vacuum chamber, a very small amount of a mixed gas of Ar, N 2 and/or O 2 is circulated to a predetermined vacuum pressure, and a voltage is applied to a target made of a simple substance of a non-gas element or a composite of non-gas elements to carry out discharge and to have the punched out non-gas element simple substance or composite reacted with N 2 and/or O 2 to form a nitride, oxide or oxynitride thereby to carry out film forming.
  • a reactive sputtering method wherein in a vacuum chamber, a very small amount of a mixed gas of Ar, N 2 and/or O 2 is circulated to a predetermined vacuum pressure, and a voltage is applied to a target made of a simple substance of a non-gas element or a composite of non-gas elements to carry out discharge and to have the punched out non-gas element simple
  • the degree of nitrification or the oxidizing amount can be changed by changing the N 2 partial pressure and/or the O 2 partial pressure of the mixed gas of Ar, N 2 and/or O 2 circulated in the vacuum chamber.
  • the non-gas elements contained in the first diffusion preventing layer 10 and the second diffusion preventing layer 11, respectively are made to be the same, whereby the first diffusion preventing layer 10 and the second diffusion preventing layer 11 can be continuously formed in the same chamber by using the same target, and the production can be facilitated.
  • the flow rate of N 2 /(Ar+N 2 ) at the time of forming the first diffusion preventing layer is usually at most 0.5, preferably at most 0.4, more preferably at most 0.3, further preferably at most 0.2, particularly preferably at most 0.1.
  • the flow rate of N 2 /(Ar+N 2 ) for forming the first diffusion preventing layer is usually at least 0.01. Within such a range, the content (atomic%) of nitrogen in the first diffusion preventing layer can be made to a desired level.
  • the flow rate of N 2 /(Ar+N 2 ) at the time of forming the second diffusion preventing layer is usually at least 0.3, preferably at least 0.4, more preferably at least 0.5.
  • the flow rate of N 2 /(Ar+N 2 ) at the time of forming the second diffusion preventing layer is usually at most 0.8. Within such a range, the content (atomic%) of nitrogen in the second diffusion preventing layer can be made to the desired level.
  • the first diffusion preventing layer 10 and the second diffusion preventing layer 11 may be formed on each side of the recording layer 3. Namely, with the layered structure of the protective layer 2, the second diffusion preventing layer 11, the first diffusion preventing layer 10, the recording layer 3, the first diffusion preventing layer 10, the second diffusion preventing layer 11 and the protective layer 4, it is possible to satisfy the rewriting cyclability and the storage stability at a very high level.
  • each of the first diffusion preventing layer and the second diffusion preventing layer contains Ge, Cr and N
  • the content (atomic%) of N contained in the second diffusion preventing layer is larger than the content (atomic%) of N contained in the first diffusion preventing layer
  • the protective layer containing ZnS is formed in contact with the second diffusion preventing layer.
  • the protective layer is composed mainly of ZnS-SiO 2
  • the recording layer is composed mainly of a composition in the vicinity of Sb 0 . 7 Te 0 .
  • the first diffusion preventing layer 10 and the second diffusion preventing layer 11 GeCrN is employed as the material, and the nitrogen content in the first diffusion preventing layer 10 is made small, and the nitrogen content in the second diffusion preventing layer 11 is made to be large.
  • the diffusion preventing layer is made into two layers, and the nitriding, oxidizing or oxynitriding degree of the first diffusion preventing layer 10 is made small to suppress peeling at the interface with the recording layer, while the nitriding, oxidizing or oxynitriding degree of the second diffusion preventing layer 11 in contact with the protective layer is made large to suppress diffusion of constituting elements at the interface with the protective layer, whereby it becomes possible to improve the rewriting cyclability and the storage stability at the same time.
  • a resin such as polycarbonate, acryl or polyolefin, or glass may be used.
  • a polycarbonate resin is most widely used for CD, and it is inexpensive and thus most preferred.
  • a film side incident type optical recording medium is employed, whereby the substrate 1 is not required to be transparent to the laser beam.
  • the thickness of the substrate is usually at least 0.1 mm, preferably at least 0.3 mm, and on the other hand, it is usually at most 3.0 mm, preferably at most 1.5 mm. Usually, it is about 1.2 mm or 0.6 mm.
  • the protective layer 2 and the protective layer 4 in Fig. 3 play a role of preventing diffusion of heat generated during the phase change in the recording layer, to another layer such as a substrate, a role of controlling the reflectance of the optical recording medium, or a role as a barrier layer to shield moisture in a storage test under a high temperature and high humidity condition.
  • Different materials may be used for the protective layer 2 and the protective layer 4, but from the viewpoint of productivity, it is preferred to use the same material.
  • the material to form the protective layers may usually be a dielectric material.
  • a dielectric material may, for example, be an oxide of Sc, Y, Ce, La, Ti, Zr, Hf, V, Nb, Ta, Zn, Al, Cr, In, Si, Ge, Sn, Sb, Te or the like, a nitride of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Zn, B, Al, Ga, In, Si, Ge, Sn, Sb, Pb or the like, a carbide of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Zn, B, Al, Ga, In, Si or the like, or a mixture thereof.
  • such a dielectric material may also be a sulfide, selenide or telluride of Zn, Y, Cd, Ga, In, Si, Ge, Sn, Pb, Sb, Bi or the like, a fluoride of Mg, Ca or the like, or a mixture thereof.
  • ZnS-SiO 2 SiN, SiO 2 , TiO 2 , CrN, TaS 2 or Y 2 O 2 S may, for example, be mentioned.
  • ZnS-SiO 2 is most widely used in view of the film-forming speed, a small film stress, a small volume change by a temperature change and excellent storage stability.
  • ZnS-SiO 2 contains a sulfur atom which is reactive with the recording layer. Therefore, when the present invention is applied to a case where this material is used as the protective layer, the effect of the present invention will most remarkably be obtained.
  • one containing sulfur may, for example, be TaS 2 or Y 2 O 2 S, Also in a case where such a material is employed, the effect of the present invention will remarkably be obtained.
  • the protective layer formed in contact with the diffusion preventing layer on the side of the recording layer opposite to the substrate side is one containing sulfur, and accordingly, in the protective layer 4 formed on the second diffusion preventing layer 11 in Figs. 3(a) to (d) , the above material containing sulfur is to be incorporated.
  • the thickness of the protective layer varies depending upon the position where the protective layer is employed in the optical recording medium.
  • the thickness of the protective layer is preferably at least 2 nm so that the effect for preventing deformation of the recording layer will be sufficient, and it will function as a protective layer.
  • the thickness is preferably at most 500 nm in order to prevent cracking by reducing the internal stress of the dielectric itself constituting the protective layer or by reducing the difference in the elastic properties from the film in contact therewith.
  • the material to constitute a protective layer has a small film-forming rate and requires a long film-forming time.
  • the thickness of the protective layer is preferably at most 300 nm, more preferably at most 200 nm.
  • the function required for a protective layer varies depending upon the position where the protective layer is used in an optical recording medium, and accordingly, the thickness will also varies depending upon the position where the protective layer is employed.
  • the thickness of the protective layer 4 in Figs. 3(a) to (d) is usually at least 10 nm, preferably at least 20 nm, more preferably at least 30 nm. Within such a range, the effect for suppressing deformation by heat of the substrate or the recording layer will be sufficient, and the role of the protective layer will be sufficiently be performed. On the other hand, the thickness of the protective layer 4 is usually at most 500 nm, preferably at most 300 nm, more preferably at most 200 nm. If the thickness is too thick, cracking is likely to result due to an internal stress of the film itself, and the productivity will also be poor. Within the above-mentioned range, prevention of cracking and the productivity can be maintained satisfactorily.
  • the film thickness d is preferably at least ⁇ /2n, where n is the refractive index of the protective layer, and ⁇ is the wavelength of the incident light.
  • the thickness of the protective layer may be selected so that the medium will have a proper reflectance due to a multiple interference effect of the incident light, and the reflectance will be periodic with ⁇ /2n to the thickness d. Further, by making the thickness of the protective layer thick, it will be possible to shield moisture penetrating into the optical recording medium, and thus, the thicker the thickness, the better the storage stability.
  • the thickness d is preferably at most ⁇ /n.
  • the thickness d is preferably within a range of at least ⁇ /2n and at most ⁇ /n.
  • the thickness of the protective layer 2 in Figs. 3(a) to (c) is usually at least 2 nm, preferably at least 4 nm, more preferably at least 6 nm. Within such a range, deformation of the recording layer can effectively be suppressed. On the other hand, the thickness of the protective layer 2 is usually at most 60 nm, preferably at most 30 nm. Within such a range, there will be no accumulation of microscopic plastic deformation in the interior of the protective layer during repetitive rewriting. Further, the cooling rate of the recording layer will sufficiently be secured.
  • the protective layer is usually formed by a sputtering method, and the total amount of impurities is preferably less than 2 atomic%, including the amount of impurities of the target itself and the amount of moisture or oxygen included during the film forming.
  • the ultimate vacuum degree of the process chamber is preferably less than 1x10 -3 Pa.
  • the protective layer 2 on the side of the recording layer 3 opposite to the protective layer 4 located via the first diffusion preventing layer 10 and the second diffusion preventing layer 11, may be replaced by an interface layer 8 having a uniform composition with the same material (such as GeCrN) as the first diffusion preventing layer 10 and the second diffusion preventing layer 11.
  • the recording layer 3 in Fig. 3 is not particularly limited so long as it is a material capable of phase change between a crystalline phase and an amorphous phase.
  • a material capable of phase change between a crystalline phase and an amorphous phase for example, in addition to an alloy made of In-Ge-Sb-Te, a Ge 2 Sb 2 Te 2 type having a composition in the vicinity of an intermetallic compound, or various materials such as Te-Sn-Ge, Te-Sb-Ge-Sn, Te-Sn-Ge-Se, Te-Sn-Ge-Au, Ag-In-Sb-Te, In-Sb-Se and In-Te-Se, may be employed.
  • compositions for the recording layer in already commercially developed phase change type optical recording media a composition in the vicinity of Ge 2 Sb 2 Te 5 as a composition in the vicinity of an intermetallic compound, and a composition in the vicinity of eutectic Sb 0.7 Te 0.3 (Sb 0.7 Te 0.3 may sometimes be represented by Sb 70 Te 30 ) of Sb 2 Te 3 -Sb, such as an In-Ge-Sb-Te type or an Ag-In-Sb-Te type, are mainly used.
  • the phase change recording material comprising Sb as the main component like the composition in the vicinity of eutectic Sb 0.7 Te 0.3 , is known to show excellent characteristics even when the recording density is made high ( Technical Digest ISOM/ODS'99 (1999) (SPIE Vol. 3864) p.191-193 ). This is considered such that the composition in the vicinity of Sb 0.7 Te 0.3 is in the vicinity of a eutectic point, whereby the crystal grain size can be made small, and the size and shape of a record mark can be controlled with a high precision.
  • the optical recording medium wherein a composition in the vicinity of Ge 2 Sb 2 Te 5 was used for the recording layer, and changing the proportion of nitrogen of GeCrN in detail.
  • the optical recording medium wherein the composition in the vicinity of Ge 2 Sb 2 Te 5 was used for the recording layer showed excellent storage stability in a high temperature and high humidity environment even in a case where the nitrogen content in the diffusion preventing layer was changed within a wide range.
  • the optical recording medium wherein the composition in the vicinity of eutectic Sb 0.7 Te 0.3 was used for the recording layer, showed peeling between the diffusion preventing layer and the recording layer in a high temperature and high humidity environment in a range other than the range where the nitrogen proportion in the diffusion preventing layer is low. And, in the range where the nitrogen proportion was low so that no peeling was observed, it was not possible to make the rewriting cyclability to be satisfactory.
  • the recording layer material employing the composition in the vicinity of Ge 2 Sb 2 Te 5 wherein Ge is contained in a larger amount in the recording layer material will have a high affinity between the recording layer material and the material for the diffusion preventing layer.
  • the composition of the recording layer is made to be a composition containing Sb as the main component like the composition in the vicinity of eutectic Sb 0.7 Te 0.3 , by constituting the diffusion preventing layer by at least two layers, it becomes possible to distinctly obtain the effects of the present invention to prevent peeling between the diffusion preventing layer and the recording layer, while maintaining rewriting cyclability.
  • the composition of the recording layer is preferably one containing Sb as the main component in the present invention, although it is not particularly limited so long as it is one commonly used for a recording layer in a phase change type optical recording medium.
  • the recording layer contains Sb as the main component means that the content of Sb in the entire recording layer is at least 50 atomic%.
  • the recording layer wherein the material containing Sb as the main component is used also has a merit that crystallization can be carried out at a very high speed, and erasing by crystallization in a short time of an amorphous mark will be possible.
  • the material containing Sb as the main component, contained in the recording layer is preferably at least 60 atomic%, more preferably at least 70 atomic%, further preferably at least 80 atomic%, particularly preferably at least 90 atomic%, most preferably at least 95 atomic%, in the entire recording layer.
  • the higher the content the more remarkable the effect of the present invention. Even if other components such as oxygen, nitrogen, etc. are included during film formation of the recording layer, good recording characteristics can still be obtained, if such other components are within a range of from a few atomic% to 20 atomic%.
  • an additional element to accelerate formation of an amorphous state and to stabilize the amorphous state, in an amount of at least 1 atomic%, preferably at least 5 atomic%, more preferably at least 10 atomic%, in the entire recording layer.
  • such an additional element is usually at most 30 atomic%.
  • the above additional element to accelerate the formation of an amorphous state and to increase the stability with time of the amorphous state also has an effect to increase the crystallization temperature.
  • at least one selected from the group consisting of Ge, Te, In, Ga and Sn is preferred with a view to accelerating formation of an amorphous state, improving the stability with time of the amorphous state and increasing the crystallization temperature.
  • Particularly preferred is to employ Ge and/or Te, or to employ at least one of In, Ga and Sn.
  • the total content of Ge and/or Te is usually at least 1 atomic%, preferably at least 3 atomic%, more preferably at least 5 atomic%, and on the other hand, the total content is preferably at most 40 atomic%, more preferably at most 35 atomic%, further preferably at most 30 atomic%, particularly preferably at most 20 atomic%, most preferably at most 15 atomic%.
  • the effect to stabilize the amorphous mark may become inadequate, and if Ge and/or Te exceeds the above range, the amorphous state tends to be too stable, whereby crystallization inversely tends to be too slow.
  • the composition containing Sb as the main component may be classified into two types depending upon the amount of Te contained in the recording layer.
  • One is a composition containing at least 10 atomic% of Te, and the other is a composition containing less than 10 atomic% of Te (inclusive of a case where no Te is contained).
  • SbTe eutectic system is preferably at least 3, more preferably at least 4.
  • the other composition containing Sb as the main component which can be classified depending upon the amount of Te contained in the recording layer, may, for example, be the following one. Namely, the composition of the recording layer is made such that while Sb is the main component, Te is made less than 10 atomic%, and Ge is incorporated as an essential component.
  • a composition for the recording layer an alloy containing a eutectic alloy having a composition in the vicinity of Sb 90 Ge 10 , as the main component, and containing Te in an amount of less than 10 atomic% (in this specification, such an alloy will be referred to as a SbGe eutectic system) may be mentioned as preferred.
  • the composition wherein the amount of Te is less than 10 atomic% is not a SbTe eutectic system and tends to have a nature as a SbGe eutectic system.
  • a SbGe eutectic alloy even if the Ge content is as high as 10 atomic%, the crystal grain size in a polycrystalline state after the initial crystallization is relatively fine, whereby the crystal state tends to be a single phase, and the noise is low.
  • Te is added merely additionally, and will not be an essential element.
  • the recording layer containing Sb as the main component such as the above-mentioned SbTe eutectic system or SbGe eutectic system
  • Sb is added excessively beyond the vicinity of the Sb 70 Te 30 eutectic point or the Sb 90 Ge 10 eutectic point to increase the crystallization speed by increasing the crystal growth rate rather than the crystal nuclei forming rate.
  • the composition for the recording layer it is particularly preferred to employ Ag or an Ag alloy having a high heat dissipation property for the reflective layer.
  • the above-mentioned recording layer employing a composition containing Sb as the main component, such as the SbTe eutectic system or the SbGe eutectic system, further contains at least one of In, Ga and Sn, and the content of each of In, Ga and Sn in the recording layer is at least 1 atomic% and at most 30 atomic%.
  • composition containing Sb as the main component will be further described.
  • the composition in the vicinity of eutectic Sb 0.7 Te 0.3 of Sb 2 Te 3 -Sb is very effective to obtain an optical recording medium for high densification and high speed recording, but it tends to be remarkable that the balance of rewriting cyclability and the storage stability of the optical recording medium can not be taken at a high level. Accordingly, the effect of the present invention wherein the diffusion preventing layer is divided into two layers to separate the functions, will be remarkable in the case of employing a recording layer containing, as the main component, the composition in the vicinity of eutectic Sb 0.7 Te 0.3 of Sb 2 Te 3 -Sb.
  • the composition in the vicinity of Sb 0.7 Te 0.3 may, for example, be a composition of (Sb x Te 1-x ) 1-y M y (wherein 0.6 ⁇ x ⁇ 0.9, 0.5 ⁇ 1-y ⁇ 1, and M is at least one element selected from Ge, Ag, In, Ga, Zn, Sn, Si, Cu, Au, Pd, Pt, Pb, Cr, Co, N, O, S, Se, V, Nb, a rare earth element, Zr, Hf and Ta).
  • a recording layer composed mainly of this composition is stable either in a crystalline state or in an amorphous state and is capable of phase change at a high speed between the two states.
  • M is particularly preferably Ge, In, Ga or Sn, most preferably Ge, from the viewpoint of the recording characteristics such as overwriting characteristics.
  • x is usually at least 0.6, preferably at least 0.7, more preferably at least 0.75 and on the other hand, it is usually at most 0.9.
  • 1-y is usually at least 0.5, preferably at least 0.7, more preferably at least 0.8, particularly preferably at least 0.9, and on the other hand, it is usually at most 1, preferably at most 0.99, more preferably at most 0.97.
  • the amount of Ge is usually at most 0.06, preferably at most 0.05, more preferably at most 0.04 as the value of y in Ge y (Sb x Te 1-x ) 1-y .
  • the above GeSbTe eutectic composition it is particularly preferred to incorporate In, Ga or Sn.
  • a composition represented by M1 z Ge y (Sb x Te 1-x ) 1-y-z (wherein 0.01 ⁇ z ⁇ 0.4, 0.01 ⁇ y ⁇ 0.06, 0.82 ⁇ x ⁇ 0.9, and M1 is at least one element selected from the group consisting of In, Ga and Sn).
  • M1 is at least one element selected from the group consisting of In, Ga and Sn.
  • z representing the content of M1 is usually at least 0.01, preferably at least 0.02, more preferably at least 0.05, and on the other hand, it is usually at most 0.4, preferably at most 0.3, more preferably at most 0.2, particularly preferably at most 0.1. Within such a range, the above-mentioned effect for improving the characteristics will be satisfactorily obtained.
  • elements which may be incorporated in addition to In, Ga and Sn may be nitrogen, oxygen and sulfur. These elements are effective to prevent segregation during repeated overwriting or to carry out fine adjustment of optical characteristics.
  • the content of nitrogen, oxygen and sulfur is more preferably at most 5 atomic%, based on the total amount of Sb, Te and Ge.
  • Cu, Zr, Hf, V, Nb, Ta, Cr or Co may be incorporated to the above GeSbTe eutectic composition.
  • Such an element is effective as added in a very small amount to increase the crystallization temperature and to further improve the stability with time, without decreasing the crystal growth rate.
  • the amount is preferably at most 5 atomic%, particularly preferably at most 3 atomic%. If segregation takes place, the recrystallization rate or the stability of the amorphous state which the recording layer initially has, may change and the overwriting characteristics may deteriorate.
  • Another preferred composition of the material for the recording layer wherein Sb is the main component and Ge and/or Te is used in combination is preferably another type of an alloy containing Sb as the main component, wherein Te is less than 10 atomic% in the entire recording layer (inclusive of a case where no Te is contained), and Ge is contained as an essential component. Namely, it is a material which can be regarded as an alloy wherein an eutectic alloy having a composition in the vicinity of Ge 10 Sb 90 , is the main component (i.e. a SbGe type eutectic alloy).
  • the present inventors By a study made by the present inventors, it has been found that with the SbTe type eutectic alloy, high speed crystallization is possible, and nevertheless, the amorphous mark is further stable than the above-mentioned GeSbTe eutectic system. Further, it has been also found to have characteristics such that it is free from an increase of the noise which is observed when the Sb/Te ratio is increased with the above GeSbTe eutectic system, whereby recording with a low noise will be possible. In a case where such a SbGe type eutectic alloy is made to be the main component, the content of Ge is preferably at least 3 atomic% and at most 30 atomic%, in the entire recording layer.
  • a three element alloy of InGeSb, GaGeSb or SnGeSb type having In, Ga or Sn added is employed as the main component.
  • In, Ga and Sn have remarkable effects to increase the difference in optical characteristics between the crystalline state and the amorphous state, than the SbGe type eutectic alloy, and they are particularly effective to obtain a high modulation as an optical recording medium.
  • Te ⁇ M2 ⁇ (Ge ⁇ Sb 1- ⁇ ) 1- ⁇ - ⁇ (wherein 0.01 ⁇ 0.3, 0 ⁇ 0.3, 0 ⁇ 0.1, 2 ⁇ / ⁇ , 0 ⁇ + ⁇ 0.4, and M2 is at least one element selected from the group consisting of In, Ga and Sn) may be mentioned.
  • In, Ga or Sn to the SbGe type eutectic alloy, it is possible to make remarkable the effect to increase the difference in optical characteristics between the crystalline state and the amorphous state.
  • ⁇ representing the content of In and/or Ga is usually at least 0, preferably at least 0.01, more preferably at least 0.05.
  • ⁇ is usually at most 0.3, preferably at most 0.2.
  • ⁇ representing the content of Sn is usually at least 0, preferably at least 0.01, more preferably at least 0.05.
  • ⁇ is usually at most 0.3, preferably at most 0.2.
  • element M2 a plurality of elements among In, Ga and Sn may be employed, but it is particularly preferred to incorporate In and Sn.
  • the total content of these elements is usually at least 1 atomic%, preferably at least 5 atomic% and usually at most 40 atomic%, preferably at most 30 atomic%, more preferably at most 25 atomic%.
  • TeM2GeSb type composition as it contains Te, it is possible to reduce the change with time of the erasing ratio in ultrahigh speed recording.
  • ⁇ representing the content of Te is usually at least 0, preferably at least 0.01, particularly preferably at least 0.05.
  • ⁇ is usually smaller than 0.1.
  • TeM2GeSb type composition when Te and element M2 are incorporated, it is effective to control the total content thereof. Accordingly, ⁇ + ⁇ representing the content of Te and element M2 is usually larger than 0, preferably at least 0.01, more preferably at least 0.05. By adjusting ⁇ + ⁇ within the above range, the effect of incorporating Te and element M2 simultaneously will be provided satisfactorily.
  • ⁇ + ⁇ is usually at most 0.4, preferably at most 0.35, more preferably at most 0.3.
  • ⁇ / ⁇ representing the atomicity ratio of element M2 to Te is preferably at least 2.
  • Te the optical contrast tends to decrease. Accordingly, in a case where Te is to be incorporated, it is preferred to slightly increase the content of element M2 (i.e. slightly increase ⁇ ).
  • Elements which may be added to the above TeM2GeSb type composition may, for example, be Au, Ag, Pd, Pt, Si, Pb, Bi, Ta, Nb, V, Mo, a rare earth element, N and O, and they are used for e.g. fine adjustment of the optical characteristics or the crystallization speed.
  • the amount of their addition is about 10 atomic% at the maximum.
  • Te and In and/or Sn are used in combination, preferred is (p+q)/r ⁇ 2.
  • the thickness of the recording layer 3 is preferably at least 5 nm in order to obtain a sufficient optical contrast or to increase the crystallization speed to accomplish erasing of a record in a short time. Further, in order to increase the reflectance to be sufficiently high, the thickness is more preferably at least 10 nm.
  • the thickness of the recording layer is preferably at most 100 nm. More preferably, it is at most 50 nm, in order to reduce the thermal capacity and to increase the recording sensitivity. Further, it is also possible to reduce the volume change due to a phase change and to minimize the influence of the repeated volume change due to repetitive rewriting, over the recording layer itself or over the upper and lower protective layers. Further, accumulation of irreversible microscopic deformation can be suppressed, whereby the noise will be reduced, and the repetitive rewriting durability will be improved.
  • the thickness of the recording layer is made more preferably at most. 30 nm.
  • the above recording layer 3 is, in many cases, obtained by sputtering an alloy target in an inert gas, particularly Ar gas. Further, the thicknesses of the recording layer and the protective layers are selected so that the absorption efficiency of a laser beam is excellent, and the amplitude of the record signal, i.e. the contrast between the recorded state and the non-recorded state, becomes large, in consideration of the interference effect due to a multilayered construction in addition to the restriction from the viewpoint the above-mentioned mechanical strength and reliability.
  • the reflective layer 5 in Figs. 3(a) to (d) in addition to Ag or an Ag alloy, various materials such as Al, Au or alloys containing them as the main components, may be employed.
  • the material for the reflective layer it is preferred to employ an alloy containing Ag or Al as the main component, which has a high thermal conductivity and a large heat dissipation effect.
  • the content of Ag or Al in the reflective layer containing Ag or Al as the main component is usually at least 50 atomic%, preferably at least 80 atomic%, more preferably at least 90 atomic%, particularly preferably at least 95 atomic%.
  • the reflective layer containing Ag as the main component it is possible to increase the thermal conductivity of the reflective layer by increasing the content of Ag. Accordingly, in order to further increase the thermal conductivity, only Ag (pure silver) may be employed for the reflective layer.
  • the material for the reflective layer suitable for the present invention is more specifically described, pure Ag, or an Ag alloy which contains, in addition to Ag, at least one element selected from the group consisting of Ti, V, Ta, Nb, W, Co, Cr, Si, Ge, Sn, Sc, Hf, Pd, Rh, Au, Pt, Mg, Zr, Mo, Cu, Nd and Mn, may be mentioned.
  • the additive component is preferably Ti, Mg, Au, Cu, Nd or Pd.
  • the material for the reflective layer may be an Al alloy containing, in addition to Al, at least one element selected from the group consisting of Ta, Ti, Co, Cr, Si, Sc, Hf, Pd, Pt, Mg, Zr, Mo and Mn.
  • Al alloy containing, in addition to Al, at least one element selected from the group consisting of Ta, Ti, Co, Cr, Si, Sc, Hf, Pd, Pt, Mg, Zr, Mo and Mn.
  • the amount of such other elements to be incorporated to Ag or Al is usually at least 0.1 atomic%, preferably at least 0.2 atomic%. With respect to the Al alloy, if the content of such elements is too little, the Hirock resistance tends to be inadequate in many cases, although such depends also on the film-forming condition. On the other hand, the content of such elements is usually at most 5 atomic%, preferably at most 2 atomic%, more preferably at most 1 atomic%. If the amount is too much, the resistivity of the reflective layer may sometimes become high (the thermal conductivity may sometimes decrease).
  • an Al alloy containing from 0 to 2 wt% of Si, from 0.5 to 2 wt% of Mg and from 0 to 0.2 wt% of Ti.
  • Si is effective to suppress fine peeling defects, but if the content is too much, the thermal conductivity may change with time. Therefore, it is usually at most 2 wt%, preferably at most 1.5 wt%.
  • Mg improves the corrosion resistance of the reflective layer, but if the content is too much, the thermal conductivity may change with time. Accordingly, it is usually at most 2 wt%, preferably at most 1.5 wt%.
  • Ti is effective to prevent fluctuation of the sputtering rate, but if the content is too much, the thermal conductivity will be lowered, and it tends to be difficult to cast a bulk in which Ti is microscopically uniformly solid-solubilized, and the target cost will be increased. Therefore, it is usually at most 0.2 wt%.
  • the thickness of the reflective layer is usually at least 40 nm, preferably at least 50 nm, and on the other hand, it is usually at most 300 nm, preferably at most 200 nm. If it is too thick, not only no adequate heat dissipation effect can be obtained, but also the recording sensitivity tends to deteriorate, although the sheet resistivity may be lowered. It is considered that with a thick film, the thermal capacity per unit area will increase, and heat dissipation of itself will take time, whereby the heat dissipation effect rather tends to be small. Further, with such a thick film, it takes time for film formation, and also the material cost tends to increase. On the other hand, if the film thickness is too thin, an influence of an island structure at the initial stage of the film growth is likely to partially observed, whereby the reflectance or the thermal conductivity may decrease.
  • the reflective layer is usually formed by a sputtering method or a vacuum vapor deposition method.
  • the total amount of impurities is preferably less than 2 atomic% including the amount of impurities of the target or the vapor deposition material itself, and the amount of moisture or oxygen included during the film forming.
  • the ultimate vacuum degree of the process chamber is preferably less than 1 ⁇ 10 -3 Pa.
  • an intentional additive element is incorporated more than 1 atomic%, it is advisable to adjust the film forming rate to be at least 10 nm/sec thereby to minimize inclusion of additional impurities.
  • At least one layer is made of a material containing the above Ag or Al having a thickness of at least 50% of the total thickness of the reflective layer. This layer substantially serves to provide the heat dissipation effect, and other layer is constructed to contribute to the corrosion resistance, adhesion with the protective layer and improvement of the Hirock resistance.
  • the light transmitting layer 9 in Figs. 3(a) to (d) is required to protect the sputtered film from moisture or dust and at the same time to serve as a thin incident substrate. Accordingly, it is desired to be transparent to a laser beam to be used for recording and retrieving, and at the same time, its thickness is preferably from 50 ⁇ m to 150 ⁇ m, and it preferably realizes a uniform thickness distribution of within 5 ⁇ m in the optical recording medium.
  • the light transmitting layer 9 is usually formed by a method wherein an uncured photocurable resin is coated by a spin coating method, followed by curing by irradiation with light, or a method of bonding a transparent sheet.
  • an ultraviolet curable resin of an acrylate type is preferred, which is excellent from the viewpoint of the stability, water resistance, curing property or low shrinkage during the curing.
  • the transparent sheet it is preferred to employ one made of a polycarbonate, which is excellent from the viewpoint of the transparency, flatness or price.
  • Fig. 3(b) is one having an under layer 12 formed between the substrate 1 and the reflective layer 5 in the structure shown in Fig. 3(a) .
  • the under layer 12 has an effect to suppress peeling between the substrate 1 and the metal reflective layer 5, whereby it will be possible to obtain a medium having excellent storage stability. Accordingly, it is preferred to form the under layer 12 between the substrate and the reflective layer. As mentioned above, the under layer 12 is formed for the purpose of suppressing peeling at the interface between the substrate 1 and the reflective layer 5 resulting at the time of the temperature change. Accordingly, its material is not particularly limited so long as it satisfies such an object. However, it is preferably one which has excellent adhesion to the substrate and the reflective layer, will not corrode the reflective layer, will not diffuse in the reflective layer and is excellent in flatness of the formed film surface.
  • a metal may be optionally selected for use from single substances or mixtures of a metal, a semiconductor, a metal oxide, a metal nitride, a metal carbide, a semiconductor oxide, a semiconductor nitride, a semiconductor carbonate, a fluoride, an amorphous carbon, etc.
  • At least one element selected from the group consisting of Si, Ti, Cr, Ta, Nb, Pd, Ni, Co, Mo and W may, for example, be mentioned.
  • Cr, Ta, Nb, Ni or Mo is preferred, and it is more preferred to employ Ta, Nb or Mo.
  • a rare earth element oxide, TiN, CrN, CaF 2 or MgF 2 may, for example, be mentioned.
  • SiN, GeN, ZnO, Nb 2 O 5 or CrN is preferred, and it is more preferred to employ GeN or CrN. It is particularly preferred to employ GeN and CrN simultaneously.
  • a typical example employing Ge-N may be one containing Al, B, Ba, Bi, C, Ca, Ce, Cr, Dy, Eu, Ga, In, K, La, Mo, Nb, Ni, Pb, Pd, Si, Sb, Sn, Ta, Te, Ti, V, W, Yb, Zn, Zr or the like together with Ge, such as Ge-Si-N, Ge-Sb-N, Ge-Cr-N, Ge-Al-N, Ge-Mo-N or Ge-Ti-N. Among them, it is preferred to employ Ge-Cr-N.
  • the under layer may not necessarily of a single layer structure made of a single material, and it may be a multilayer structure having a plurality of materials coated.
  • a double layered structure having a mixture of ZnS-SiO 2 and GeCeN on a substrate may be mentioned.
  • ZnS-SiO 2 is excellent in adhesion with the substrate, and further by the presence of GeCrN, corrosion of silver by sulfur in ZnS-SiO 2 can be prevented even in a case where silver or a silver alloy is employed for the reflective layer.
  • the under layer 12 is sufficient in a thickness which can be uniformly formed on the substrate 1, and on the contrary, if it becomes thick, not only the production cost and the production time will increase, but also a change in the groove shape of the substrate, or the like, will result. Accordingly, the thickness is preferably from 2 nm to 20 nm. Further, like other layers, the under layer is prepared by sputtering or reactive sputtering.
  • the structure of the optical recording medium in Figs. 3(a) to (d) is not limited to the above described structures, but may be applied to various structures, such as a structure wherein a layer made of another material may be formed between the reflective layer 5 and the protective layer 2 or the interface layer 8 as a substitute for the protective layer, or a structure wherein the reflective layer is constituted by double layers.
  • the optical recording medium in the second embodiment of the present invention is an optical recording medium comprising a reflective layer and a phase change recording layer formed in this order on a substrate, so that recording and retrieving information is carried out by applying a laser beam to the phase change recording layer from the side of the phase change recording layer opposite to the substrate side, characterized in that:
  • the diffusion preventing layer is divided into two layers, so that the respective diffusion preventing layers have separate functions, thereby to obtain an optical recording medium excellent in rewriting cyclability and storage stability.
  • the diffusion preventing layer is provided with a function required for the relation with the recording layer and a function required for the relation with the protective layer by changing the composition at the interface with the recording layer and the composition at the interface with the protective layer.
  • the interface between the diffusion preventing layer and the protective layer is a region up to 1 nm on the diffusion preventing layer side from the plane where the diffusion preventing layer is in contact with the protective layer. Further, the interface between the diffusion preventing layer and the phase change recording layer is a region up to 1 nm on the diffusion preventing layer side from the plane where the diffusion preventing layer is in contact with the recording layer.
  • Fig. 4 is a diagrammatical view showing an example of the layered structure of a preferred optical recording medium in the second embodiment of the present invention.
  • the optical recording medium in Fig. 4 comprises a reflective layer 5, a protective layer 2, a recording layer 3, a diffusion preventing layer 7, a protective layer 4 and a light transmitting layer 9 laminated in this order on a substrate 1, and a laser beam 100 to be applied to the optical recording medium from the upper side of the light transmitting layer 9.
  • the effects of the present invention are remarkably observed in a film side incident type optical recording medium, as explained in the above "first embodiment of the present invention". Further, the materials, thicknesses and production methods of the respective layers of the substrate 1, the reflective layer 5, the protective layer 2, the recording layer 3, the protective layer 4 and the light transmitting layer 9, in Fig. 4 , are as described in the above "first embodiment of the present invention", and the same ones as in the first embodiment of the present invention may be employed.
  • an under layer may be inserted between the substrate 1 and the reflective layer 5, or the protective layer 2 may be substituted by an interface layer 8 of a single composition.
  • the diffusion preventing layer 7 comprises a non-gas element and nitrogen and/or oxygen as the main components.
  • the non-gas element, or the material constituted by the non-gas element and nitrogen and/or oxygen is as described in the above "first embodiment of the present invention".
  • the total content of the non-gas element and nitrogen and/or oxygen in the diffusion preventing layer 7 is usually at least 70 atomic%, preferably at least 90 atomic%, more preferably at least 95 atomic%, most preferably at least 99 atomic%. In this manner, peeling from the recording layer can effectively be prevented, and rewriting cyclability can be improved.
  • the content of such elements is preferably at most 10 atomic%, more preferably at most 5 atomic%, particularly preferably at most 1 atomic%. Further, such elements are not particularly limited, but in a case of an element having a nature of diffusing into a layer, such as sulfur, its content is preferably at most 1 atomic%.
  • the content of nitrogen and/or oxygen at the interface between the diffusion preventing layer 7 and the recording layer 3, is usually at least 3 atomic%, preferably at least 5 atomic%, more preferably at least 10 atomic%. Within such a range, it becomes possible to reduce the optical absorption.
  • the content of nitrogen and/or oxygen at the interface between the diffusion preventing layer 7 and the recording layer 3 is usually at most 50 atomic%, preferably at most 45 atomic%, more preferably at most 40 atomic%. Within such a range, it becomes possible to prevent peeling between the recording layer and the diffusion preventing layer.
  • the content of nitrogen and/or oxygen at the interface between the diffusion preventing layer 7 and the protective layer 4 is usually at least 40 atomic%, and on the other hand, usually at most 70 atomic%, preferably at most 65 atomic%, more preferably at most 60 atomic%. Within such a range, it becomes possible to suppress the chemical reaction and diffusion of constituting atoms between the protective layer and the diffusion preventing layer.
  • the content (atomic%) of nitrogen and/or oxygen at the interface of the diffusion preventing layer 7 and the protective layer 4 is made to be larger than the content (atomic%) of nitrogen and/or oxygen at the interface between the diffusion preventing layer 7 and the recording layer 3.
  • the content of nitrogen and/or oxygen may be made to be constant. Further, in a region of the diffusion preventing layer 7 other than the interface between the diffusion preventing layer 7 and the protective layer 4 and the interface between the diffusion preventing layer 7 and the recording layer 3, the content of nitrogen and/or oxygen may continuously or stepwisely be changed in the thickness direction of the diffusion preventing layer. Preferred among them is that the content of nitrogen and/or oxygen is continuously or stepwisely changed in the thickness direction of the diffusion preventing layer.
  • the ratio in the content of the nitrogen and/or oxygen as between at the interface between the diffusion preventing layer 7 and the recording layer 3 and at the interface between the diffusion preventing layer 7 and the protective layer 4, i.e. (the content of nitrogen and/or oxygen at the interface between the diffusion preventing layer 7 and the recording layer 3)/(the content of nitrogen and/or oxygen at the interface between diffusion preventing layer 7 and the protective layer 4), is usually smaller than 1, preferably at most 0.8, more preferably at most 0.6, further preferably at most 0.5, most preferably at most 0.4. Within such a range, the balance of the storage stability and the rewriting cyclability of the optical recording medium will be good.
  • the analysis of the composition of the above diffusion preventing layer 7 can be made by a combination of an Auger electron spectrophotometry (AES), a Rutherford backscattering method (RBS), an induction coupling high frequency plasma photometry (ICP). And, by the above analysis of the composition, the content (atomic%) of nitrogen and/or oxygen at the interface between the diffusion preventing layer 7 and the recording layer 3, and the content (atomic%) of nitrogen and/or oxygen at the interface between the diffusion preventing layer 7 and the protective layer 4, can be obtained.
  • AES Auger electron spectrophotometry
  • RBS Rutherford backscattering method
  • ICP induction coupling high frequency plasma photometry
  • the thickness of the diffusion preventing layer is usually at least 2 nm. Within such a range, it becomes possible to suppress diffusion of sulfur even in a case where ZnS-SiO 2 which is commonly used for the protective layer, is employed. Further, if the thickness is too thin, a uniform diffusion preventing layer may not be obtained.
  • the thickness of the diffusion preventing layer 7 is usually at most 10 nm, preferably at most 7 nm, more preferably at most 4 nm. Within such a range, not only it becomes possible to prevent diffusion of constituting atoms between the recording layer and the protective layer, but it becomes possible to certainly obtain a diffusion preventing layer excellent in the storage stability free from peeling by suppressing the film stress to be minimum.
  • the diffusion preventing layer 7 can be prepared by reactive sputtering employing a target made of a single substance of the non-gas element or a composite of the non-gas elements.
  • the N 2 partial pressure or the O 2 partial pressure of the mixed gas of Ar, N 2 and/or O 2 circulated in the vacuum chamber may be changed between the initial stage and the last stage, but preferably continuously changed during the film forming.
  • the flow rate of N 2 /(Ar+N 2 ) at the time of forming the interface between the diffusion preventing layer 7 in contact with the recording layer is usually at most 0.4, preferably at most 0.3, more preferably at most 0.2, most preferably at most 0.1. On the other hand, it is usually at least 0.01. Within such a range, the content (atomic%) of nitrogen at the interface between the recording layer and the diffusion preventing layer can be made to be the desired level.
  • the flow rate of N 2 /(Ar+N 2 ) at the time of forming the interface between the diffusion preventing layer 7 in contact with the protective layer is usually at least 0.3, preferably at least 0.4, more preferably at least 0.5. On the other hand, it is usually 0.8 or less. Within such a range, the content (atomic%) of nitrogen at the interface between the protective layer and the diffusion preventing layer can be made to be the desired level.
  • a specific example of such a diffusion preventing layer may, for example, be such that GeCrN is used for the diffusion preventing layer, and the proportion of the N component at the interface with the protective layer, is made larger than the proportion of the N component at the interface with the recording layer, whereby it will be possible to obtain an optical recording medium excellent in the storage stability while effectively preventing diffusion of constituting elements between the protective layer and the recording layer.
  • an optical recording medium having a structure shown in Fig. 3(d) was prepared.
  • a disk shaped polycarbonate resin having a thickness of 1.1 mm and a diameter of 120 mm was employed.
  • the protective layer 4 a mixture comprising ZnS-SiO 2 was employed.
  • an alloy comprising In-Ge-Sb-Te was employed.
  • an alloy comprising Ag-Cu-Au was employed.
  • GeCrN was employed, and further for the first diffusion preventing layer 10 and for the second diffusion preventing layer 11, GeCrN (one having the concentration of the N component changed) was employed
  • the light transmitting layer 9 With respect to the light transmitting layer 9, 2.5 g of an uncured (non-polymerized) acrylate type ultraviolet curable agent having a viscosity of 3000 mPa ⁇ s was dropped in the vicinity of the center of the protective layer 4 and stretched by rotation at 1500 rpm for 6 seconds, and then irradiated with ultraviolet rays for curing (polymerization) to form it. During irradiation with ultraviolet rays, in order to prevent the polymerization inhibiting action by oxygen, nitrogen was purged to carry out the ultraviolet radiation at an oxygen concentration of at most 5%. The thickness of the light transmitting layer 9 was adjusted to be within a range of from 95 to 105 ⁇ m. Here, for the measurement of the film thickness, the light transmitting layer was mechanically peeled after curing of the light transmitting layer 9 and measured by means of a micrometer.
  • a sputtering method was employed for the preparation of multilayered films other than the substrate 1 and the light transmitting layer 9.
  • the film forming conditions and the film thicknesses of the respective layers were as follows.
  • the phase change type optical recording medium having the above structure was designated as disk 1, and further, disks 2 to 4 were prepared which had the same structure except that in disk 1, the N 2 /(Ar+N 2 ) flow ratio in the film forming conditions for the first diffusion preventing layer 10 was changed from 0.1 to 0.2, 0.3 and 0.4.
  • Evaluation of the characteristics was carried out with respect to the storage stability and the rewriting cyclability. Evaluation of the storage stability was carried out by preparing five disks for each of disks 1 to 4, and observing the four directions of each disk in a radial direction at 0°, 90°, 180° and 270°, before and after the acceleration test.
  • the acceleration test was carried out in two ways i.e. under a condition of maintaining a sample in an environment of 80°C/85% for 250 hours and under a condition of maintaining a sample in an environment of 110°C/90% for 5 hours.
  • rewriting 30,000 times and 50,000 times was carried out by using a pickup having a numerical aperture NA of 0.85 and a wavelength of 404 nm at a linear velocity of 5.7 m/s by a RLL (1, 7) signal system in a case where the shortest mark length was 0.173 ⁇ m.
  • the record signals after rewriting 30,000 times and 50,000 times were subjected to waveform equalization by means of a waveform equalization device, and then, a value (a jitter value) obtained by dividing, by a window width T, a jitter of the difference in timing between the rising and falling of a binarized signal and the rising of a clock signal, was evaluated.
  • a phase change type optical disk having the same structure as in Example 1 was prepared except that in Fig. 3(d) the first diffusion preventing layer 10 and the second diffusion preventing layer 11 was replaced by a single diffusion preventing layer 13 having a single composition ( Fig. 2(b) ).
  • the film forming conditions and the film thickness of the diffusion preventing layer 13 were as follows.
  • the phase change type optical recording medium of the above structure was designated as disk 5, and further disks 6 to 9 having the same structure, were prepared except that the N 2 /(Ar+N 2 ) flow ratio was changed from 0.1 to 0.2, 0.3, 0.4 and 0.5.
  • GeCrN in contact with the recording layer is required to have a small N 2 /(Ar+N 2 ) flow ratio during its film formation i.e. required to have a small nitriding degree.
  • GeCrN made of a single layer, at a nitriding degree to satisfy the storage stability, it is not possible to obtain an optical recording medium which fully satisfy the rewriting cyclability.
  • the nitriding degree is large in GeCrN of the diffusion preventing layer made of a single layer, the rewriting cyclability will be good, but it is not possible to obtain an optical recording medium which satisfies the storage stability.
  • This is considered to be attributable to the fact that although diffusion of constituting elements between the diffusion preventing layer made of GeCrN and the protective layer made of ZnS-SiO 2 is suppressed, as the nitriding degree is large, the recording layer and the diffusion preventing layer are more likely to undergo peeling.
  • the effectiveness of the present invention has been made clear, such that the diffusion preventing layer of GeCrN is divided into two layers, so that the first diffusion preventing layer in contact with the recording layer has a small nitriding degree to improve the storage stability, while the second diffusion preventing layer in contact with the protective layer is made to have a large nitriding degree thereby to suppress diffusion of elements between the second diffusion preventing layer and the protective layer.
  • an optical recording medium of a structure having the under layer 12 removed from Fig. 3(d) was prepared.
  • the substrate 1 and the light transmitting layer 9 were exactly the same as in Example 1.
  • the protective layer 4 the reflective layer 5, the interface layer 8 as a substitute for the protective layer, the recording layer 3, the first diffusion preventing layer 10 and the second diffusion preventing layer 11, the same materials as in Example 1 were employed, and they were prepared by a sputtering method.
  • the film forming conditions and the film thicknesses of the respective layers are as follows.
  • disk 11 having the same structure was prepared except that in the phase change type optical disk 10 of the above structure, the thickness of the protective layer 4 was changed to 129 nm.
  • disk 12 having a layer made of GeCrN added as an under layer 12 in disk 11, or disk 13 having a layer made of Ta added was prepared.
  • the film forming conditions for each under layer 12 are as follows.
  • the layered structures of the foregoing disks 10 to 13 are shown in Table 3, and the results of evaluation of disks 10 to 13 are shown in Table 4. Evaluation of the characteristics were carried out with respect to the storage stability and rewriting cyclability. With respect to the evaluation of the storage stability, an acceleration test was carried out while maintaining the disk in an environment of 80°C/85% for 100 hours, whereby the error rate was measured. The measurement of the error rate was carried out with respect to the measurement of a signal recorded prior to the acceleration test (archival) and with respect to the measurement of a signal recorded after the acceleration test (shelf). Further, measurement of an error rate of archival was carried out by carrying out an acceleration test by maintaining a disk for three hours under an environment of 110°C/90%.
  • the archival error rate in an acceleration test at 80°C/85% was good at a level of not more than 1.0 ⁇ 10 -5 with respect to all of disks 10 to 13. Further, the shelf error rate in an acceleration test at 80°C/85% and the archival error rate in an acceleration test at 110°C/90% were better with disks 11 to 13 than with disk 10, and further, the archival error rate in an acceleration test at 110°C/90% was better with disks 12 and 13 than with disks 10 and 11. Especially disks 12 and 13 wherein an under layer was provided, and the thickness of the protective layer 4 was more than ⁇ /2n, were good with respect to all of the measured values.
  • the structure shown in Fig. 5 is a structure wherein in the structure shown in Fig. 2(a) , a diffusion preventing layer 13 made of a single layer is formed on the substrate side of the recording layer 3, and further an under layer 12 and an interface layer 14 of the reflective layer are formed.
  • the interface layer 14 of the reflective layer was formed for the purpose of preventing diffusion of constituting elements between the protective layer 2 and the reflective layer 5.
  • the substrate 1 and the light transmitting layer 9 were exactly the same as in Example 1.
  • the protective layer 4 the recording layer 3, the reflective layer 5 and the under layer 12, the same materials as in Example 1 were employed, and they were prepared by a sputtering method.
  • the film forming conditions and the film thicknesses of the respective layers are as follows.
  • the above optical recording medium was designated as disk 14, and further, disks 15 to 18 were prepared which had the same structure except that in disk 14, the N 2 /(Ar+N 2 ) flow ratio in the film forming conditions for the diffusion preventing layer 13 was changed from 0.1 to 0.2, 0.3, 0.4 and 0.5.
  • the recording layer will be formed after forming the diffusion preventing layer.
  • a vacuum evacuation step is included before formation of the recording layer, and an excess gas component (such as nitrogen or oxygen) on the diffusion preventing layer will be evacuated, and there will be no residual gas at the interface between the diffusion preventing layer and the recording layer, thus showing excellent whether resistance.
  • the protective layer located on the substrate side of the recording layer is close to the reflective layer, whereby the temperature rise is not remarkable due to the heat dissipation effect of the reflective layer, while in the protective layer located on the incident side of the recording layer, heat dissipation is inadequate, whereby the temperature rise becomes remarkable, and mutual diffusion of constituting atoms between the recording layer and the protective layer on the incident side will be the main factor for the deterioration of the rewriting cyclability.
  • the method of dividing the diffusion preventing layer into multilayers or the method of continuously changing the continuous gas element content to change the content of the gas element as between the recording layer interface and the protective layer interface will be effective for the first time when it is employed for the incident side of a film side incident type optical recording medium.
  • the present invention it is possible to obtain a film side incident type optical recording medium which simultaneously satisfies the storage stability and the repetitive recording characteristics at a higher level than ever. Particularly, it is possible to obtain a film-side incident type optical recording medium excellent in the rewriting cyclability and the storage stability when held under a high temperature and high humidity condition.
  • the present invention by separating the functions of the diffusion preventing layer formed between the recording layer and the protective layer located on the light incident side, as between the side in contact with the recording layer and the side in contact with the protective layer, it becomes possible that the storage stability and the rewriting cyclability of the optical recording medium can be satisfied at a very high level in good balance.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Optical Record Carriers And Manufacture Thereof (AREA)
  • Thermal Transfer Or Thermal Recording In General (AREA)

Claims (20)

  1. Optisches Aufzeichnungsmedium, umfassend eine Reflexionsschicht (5) und eine Phasenänderungs-Aufzeichnungsschicht (3), die in dieser Reihenfolge auf einem Substrat (1) gebildet sind, so dass Aufzeichnen und Wiederauffinden der Information durch Anlegen eines Laserstrahls (100) an die Phasenänderungs-Aufzeichnungsschicht (3) von der Seite der Phasenänderungs-Aufzeichnungsschicht (3), die der Substratseite entgegengesetzt ist, durchgeführt wird, wobei das optische Aufzeichnungsmedium ferner eine Diffusions-Verhinderungsschicht (13) umfasst, die in Kontakt mit der Phasenänderungs-Aufzeichnungsschicht (3) ist,
    dadurch gekennzeichnet, dass:
    die Diffusions-Verhinderungsschicht (13) auf der Seite der Phasenänderungs-Aufzeichnungsschicht (3) gebildet ist, die der Substratseite entgegengesetzt ist,
    eine Schutzschicht (2, 4), die Schwefel enthält, in Kontakt mit der Diffusions-Verhinderungsschicht (13) gebildet ist,
    die Diffusions-Verhinderungsschicht (13) durch mindestens zwei Schichten aufgebaut ist, die ein Nicht-Gaselement und Stickstoff und/oder Sauerstoff als Hauptkomponenten umfassen, und
    wenn von den mindestens zwei Schichten, die die Diffusions-Verhinderungsschicht (13) aufbauen, die mit der Phasenänderungs-Aufzeichnungsschicht (3) in Kontakt stehende Schicht als eine erste Diffusions-Verhinderungsschicht (10) bezeichnet wird, und die in Kontakt mit der Schutzschicht (2, 4) stehende Schicht als eine zweite Diffusions-Verhinderungsschicht (11) bezeichnet wird,
    die Menge (Atom-%) an Stickstoff und/oder Sauerstoff, die in der zweiten Diffusions-Verhinderungsschicht (11) enthalten ist, grösser als die Menge (Atom-%) an Stickstoff und/oder Sauerstoff ist, die in der ersten Diffusions-Verhinderungsschicht (10) enthalten ist.
  2. Optisches Aufzeichnungsmedium nach Anspruch 1, worin die Diffusions-Verhinderungsschicht (13) durch zwei Schichten der ersten Diffusions-Verhinderungsschicht (10) und der zweiten Diffusions-Verhinderungsschicht (11) aufgebaut ist.
  3. Optisches Aufzeichnungsmedium nach Anspruch 1 oder 2, worin das Nicht-Gaselement, das in jeder der ersten Diffusions-Verhinderungsschicht (10) und der zweiten Diffusions-Verhinderungsschicht (11) enthalten ist, das gleiche ist.
  4. Optisches Aufzeichnungsmedium nach einem der Ansprüche 1 bis 3, worin die Dicke jeder der ersten Diffusions-Verhinderungsschicht (10) und der zweiten Diffusions-Verhinderungsschicht (11) mindestens 1 nm ist.
  5. Optisches Aufzeichnungsmedium, das eine Reflexionsschicht (5) und eine Phasenänderungs-Aufzeichnungsschicht (3) umfasst, die in dieser Reihenfolge auf einem Substrat (1) gebildet sind, so dass Aufzeichnen und Wiederauffinden von Information durch Anlegen eines Laserstrahls (100) an die Phasenänderungs-Aufzeichnungsschicht (3) von der Seite der Phasenänderungs-Aufzeichnungsschicht (3), die der Substratseite entgegengesetzt ist, durchgeführt wird, wobei das optische Aufzeichnungsmedium ferner eine Diffusionsverhinderungsschicht (7) umfasst, die in Kontakt mit der Phasenänderungs-Aufzeichnungsschicht (3) steht, dadurch gekennzeichnet, dass:
    die Diffusions-Verhinderungsschicht (7) auf der Seite der Phasenänderungs-Aufzeichnungsschicht (3) gebildet ist, die der Substratseite entgegengesetzt ist,
    eine Schutzschicht (2, 4), die Schwefel enthält, in Kontakt mit der Diffusions-Verhinderungsschicht (7) gebildet ist,
    die Diffusions-Verhinderungsschicht (7) ein Nicht-Gaselement und Stickstoff und/oder Sauerstoff als Hauptkomponenten umfasst, und
    der Gehalt (Atom-%) an Stickstoff und/oder Sauerstoff an der Grenzfläche zwischen der Diffusions-Verhinderungsschicht (7) und der Schutzschicht (4) grösser als der Gehalt (Atom-%) an Stickstoff und/oder Sauerstoff an der Grenzfläche zwischen der Diffusions-Verhinderungsschicht (7) und der Phasenänderungs-Aufzeichnungsschicht (3) ist.
  6. Optisches Aufzeichnungsmedium nach Anspruch 5, worin die Dicke der Diffusions-Verhinderungsschicht (7) wenigstens 2 nm ist.
  7. Optisches Aufzeichnungsmedium nach einem der Ansprüche 1 bis 6, worin das Nicht-Gaselement mindestens eines ist, das aus der Gruppe ausgewählt ist, die aus Si, Ge, Al, Ti, Ta, Cr, Mo, Sb, Sn, Nb, Y, Zr und Hf besteht.
  8. Optisches Aufzeichnungsmedium nach Anspruch 7, worin das Nicht-Gaselement mindestens eines ist, das aus der Gruppe ausgewählt ist, die aus Si, Ge, Al und Cr besteht.
  9. Optisches Aufzeichnungsmedium nach einem der Ansprüche 1 bis 4, worin jede der ersten Diffusions-Verhinderungsschicht (10) und der zweiten Diffusions-Verhinderungsschicht (11) Ge, Cr und N enthält und der Gehalt (Atom-%) an N, der in der zweiten Diffusions-Verhinderungsschicht (11) enthalten ist, grösser als der Gehalt (Atom-%) an N ist, der in der ersten Diffusions-Verhinderungsschicht (10) enthalten ist, und eine Schutzschicht (2, 4), die ZnS enthält, in Kontakt mit der zweiten Diffusions-Verhinderungsschicht (11) gebildet ist.
  10. Optisches Aufzeichnungsmedium nach einem der Ansprüche 1 bis 9, worin die Phasenänderungs-Aufzeichnungsschicht (3) Sb als Hauptkomponente enthält.
  11. Optisches Aufzeichnungsmedium nach Anspruch 10, worin die Phasenänderungs-Aufzeichnungsschicht (3) ferner Ge und/oder Te enthält.
  12. Optisches Aufzeichnungsmedium nach Anspruch 11, worin der Gesamtgehalt an Ge und/oder Te 3 bis 40 Atom-% beträgt.
  13. Optisches Aufzeichnungsmedium nach Anspruch 10, worin die Phasenänderungs-Aufzeichnungsschicht (3) eine Zusammensetzung von (SbxTe1-x)1-yMy besitzt (worin 0,6 ≤ x ≤ 0,9, 0,5 ≤ 1-y ≤1 und M mindestens ein Element ist, das aus Ge, Ag, In, Ga, Zn, Sn, Si, Cu, Au, Pd, Pt, Pb, Cr, Co, N, O, S, Se, V, Nb, Seltenerdelemente, Zr, Hf und Ta ausgewählt ist).
  14. Optisches Aufzeichnungsmedium nach Anspruch 13, worin M mindestens eines aus Ge, Ag und In ist.
  15. Optisches Aufzeichnungsmedium nach Anspruch 10, worin die Phasenänderungs-Aufzeichnungsschicht (3) eine Zusammensetzung von TeγM2δ (GeεSb1-ε)1-δ-γ aufweist (worin 0,01 ≤ε ≤0,3, 0 ≤ δ ≤ 0,3, 0 ≤ γ ≤ 0,1, 2 ≤δ/γ, 0 < δ+γ ≤ 0,4, und M2 mindestens ein Element ist, das aus der Gruppe ausgewählt ist, die aus In, Ga und Sn besteht).
  16. Optisches Aufzeichnungsmedium nach einem der Ansprüche 1 bis 15, worin eine Unterschicht (12) zwischen dem Substrat (1) und der Reflexionsschicht (5) gebildet ist.
  17. Optisches Aufzeichnungsmedium nach Anspruch 16, worin die Unterschicht (12) mindestens ein Element enthält, das aus der Gruppe ausgewählt ist, die aus Si, Ti, Cr, Ta, Nb, Pd, Ni, Co, Mo und W besteht.
  18. Optisches Aufzeichnungsmedium nach Anspruch 16, worin die Unterschicht (12) mindestens eine Verbindung enthält, die aus der Gruppe ausgewählt ist, die aus SiN, SiO2, SiC, GeN, ZnO, Al2O3, Ta2O5, TaN, Nb2O5, ZrO2 Seltenerdelementoxiden, TiN, CrN, CaF2 und MgF2 besteht.
  19. Optisches Aufzeichnungsmedium nach Anspruch 18, worin die Unterschicht (12) GeN und CrN enthält.
  20. Optisches Aufzeichnungsmedium nach einem der Ansprüche 1 bis 19, worin d ≥ λ/2n, worin n der Brechungsindex der Schutzschicht (2, 4) ist, d die Dicke der Schutzschicht (2, 4) ist und λ die Wellenlänge des Aufzeichnungs-/Wiederauffindungs-Lichts ist.
EP03748676A 2002-10-02 2003-10-02 Optisches aufzeichnungsmedium Expired - Lifetime EP1548721B1 (de)

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Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1669988A1 (de) * 2003-09-25 2006-06-14 Ricoh Company, Ltd. Optisches aufzeichnungsmedium
JP2006155794A (ja) * 2004-11-30 2006-06-15 Tdk Corp 光記録媒体及びその試験方法
JP4403413B2 (ja) * 2005-05-11 2010-01-27 ソニー株式会社 相変化型光情報記録媒体
JP4357454B2 (ja) * 2005-06-08 2009-11-04 株式会社東芝 光記録媒体および光ディスク
JP4377877B2 (ja) * 2005-12-21 2009-12-02 ソニー株式会社 光情報記録媒体用Ａｇ合金反射膜、光情報記録媒体および光情報記録媒体用Ａｇ合金反射膜の形成用のＡｇ合金スパッタリングターゲット
JP4560495B2 (ja) 2006-06-16 2010-10-13 三菱化学メディア株式会社 記録媒体
JP4798447B2 (ja) * 2006-09-22 2011-10-19 独立行政法人産業技術総合研究所 光記録媒体
US7960006B2 (en) * 2007-01-23 2011-06-14 Tdk Corporation Optical recording medium and recording film material
KR20110055729A (ko) * 2008-09-12 2011-05-25 브라이엄 영 유니버시티 주입된 산소화 기체를 함유하는 필름 및 이의 제조 방법
KR20110061618A (ko) * 2008-09-12 2011-06-09 브라이엄 영 유니버시티 탄소 및 금속층을 포함하는 데이터 저장 매체
CN103778922A (zh) * 2014-01-25 2014-05-07 北京工业大学 紫外激光诱导相变光盘存储的一种方法
CA3147927C (en) * 2019-08-14 2023-01-24 Ceramic Data Solutions GmbH Method for long-term storage of information and storage medium therefor

Family Cites Families (27)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02123533A (ja) * 1988-11-02 1990-05-11 Nec Home Electron Ltd 光ディスクおよびその製造方法
JP3136153B2 (ja) 1990-06-19 2001-02-19 松下電器産業株式会社 光記録媒体及びその製造方法
US5194363A (en) * 1990-04-27 1993-03-16 Matsushita Electric Industrial Co., Ltd. Optical recording medium and production process for the medium
JP3078823B2 (ja) 1990-06-19 2000-08-21 松下電器産業株式会社 光記録媒体及びその製造方法
JP2926955B2 (ja) 1990-10-05 1999-07-28 日本電気株式会社 相変化型光記録媒体
JP3129497B2 (ja) * 1992-02-03 2001-01-29 株式会社リコー 相変化型光記録媒体
JP3365519B2 (ja) 1993-05-31 2003-01-14 旭化成株式会社 相変化型光ディスク
JP3612927B2 (ja) * 1997-03-31 2005-01-26 松下電器産業株式会社 光学情報記録媒体
JP3816658B2 (ja) * 1998-01-23 2006-08-30 松下電器産業株式会社 光学情報記録媒体及びその製造方法
CN100492507C (zh) * 1996-03-11 2009-05-27 松下电器产业株式会社 光学信息记录媒体及其制造方法
JPH1016393A (ja) 1996-07-03 1998-01-20 Matsushita Electric Ind Co Ltd 相変化型光学情報記録媒体及びその製造方法
JP3687264B2 (ja) 1997-04-16 2005-08-24 松下電器産業株式会社 光学式情報記録媒体及びその製造方法
US6353592B1 (en) * 1997-06-27 2002-03-05 Sony Corporation Optical recording medium and optical disk device
TW411457B (en) * 1997-08-01 2000-11-11 Hitachi Maxell Information recording medium
JPH11115315A (ja) * 1997-08-12 1999-04-27 Matsushita Electric Ind Co Ltd 光学情報記録媒体とその製造方法、及びこの媒体を用いた情報の記録再生方法
US6503690B1 (en) * 1997-08-12 2003-01-07 Matsushita Electric Industrial Co., Ltd. Optical information recording medium, method for producing the same, and method for recording and reproducing optical information
JP3570169B2 (ja) * 1997-08-22 2004-09-29 松下電器産業株式会社 光学情報記録媒体
JP3608934B2 (ja) * 1998-03-02 2005-01-12 花王株式会社 光記録媒体及び光記録媒体用保護膜
JP3250989B2 (ja) * 1998-05-15 2002-01-28 松下電器産業株式会社 光学情報記録媒体、その記録再生方法、その製造法及び光学情報記録再生装置
TW448443B (en) * 1998-08-05 2001-08-01 Matsushita Electric Ind Co Ltd Optical information storage media and production method as well as the storage reproducing method and device
JP3485040B2 (ja) * 1998-09-09 2004-01-13 三菱化学株式会社 光学的情報記録用媒体及び光記録方法
JP2000113592A (ja) 1998-10-02 2000-04-21 Toa Corp 録音装置及び連続録音装置
US6636477B1 (en) * 1998-10-07 2003-10-21 Hitachi, Ltd. Information recording medium and information recording device
JP2002074739A (ja) * 1999-10-29 2002-03-15 Toray Ind Inc 光記録媒体および光記録装置
JP4091262B2 (ja) * 2001-03-21 2008-05-28 日立マクセル株式会社 情報記録媒体および情報記録媒体の製造方法
JP3777111B2 (ja) * 2001-07-12 2006-05-24 日立マクセル株式会社 情報記録媒体および製造方法
JP2005038568A (ja) * 2003-06-26 2005-02-10 Hitachi Maxell Ltd 相変化光記録媒体

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TW200416719A (en) 2004-09-01
EP1548721A4 (de) 2008-06-11
WO2004032131A1 (ja) 2004-04-15
AU2003268736A8 (en) 2004-04-23
CN1333399C (zh) 2007-08-22
AU2003268736A1 (en) 2004-04-23
US7001655B2 (en) 2006-02-21
US20050079444A1 (en) 2005-04-14
TWI272607B (en) 2007-02-01
CN1685414A (zh) 2005-10-19
EP1548721A1 (de) 2005-06-29

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